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C06 - Multiscale structure of atmospheric vortices

Head(s): Dr. Daniel Baum (ZIB), Prof. Dr.-Ing. Rupert Klein (FU Berlin), Prof. Dr. Stephan Pfahl (FU Berlin)
Project member(s):
Participating institution(s): FU Berlin, ZIB

Project Summary

Atmospheric convection is governed by processes and scale interactions that comprise the synoptic scale (~ 1000 km), determining the environment in which convection occurs, the mesoscale (~ 100–300 km) on which different convective processes can organize, and the convective scale (~ 1–10 km) on which individual cells develop. Here we will investigate these scale interactions, focusing on frontal environments, often embedded in synoptic-scale vortical structures, that can be particularly favorable for convection. Specifically, we aim at developing a theory to describe how such frontal environments shape the properties of convective cells, and how the cumulative effects of convection in turn feed back on the evolution of the synoptic-scale front.
The project draws upon the results of the first two funding periods during which it focused on the dynamics of tropical storms and incipient hurricanes. Methods of matched and multiple-scale asymptotics were combined with numerical simulations of idealized tests and with advanced visual data analysis of high-resolution numerical reconstructions of real-life storms to test hypotheses regarding the causal mechanisms of intensification of such storms and their stabilization against background shear. This three-pronged methodological approach will be maintained during the third funding period, but now applied primarily to atmospheric flows pertaining to the middle latitudes.
One cornerstone of this work will be the project’s recent extension of the classical QGEkman layer theory to include a third “diabatic layer” of intermediate height (~ 3 km). This, in conjunction with known frontal solutions of the Smith and Stechmann’s “moist QG” model, is expected to shed new light onto the formation of weather fronts and their self-organized convection. In this context, it is expected that a frontal environment shapes the properties of convective cells, which in turn feed back on the evolution of the front itself. Solutions of the emerging reduced asymptotic model, simulations of idealized test cases and re-analyses of realistic fronts will be scrutinized by advanced techniques of visual data analysis to test this central hypothesis.
Methodology-related contributions of the project have been and will be (i) the role-out of advanced multiscale asymptotic analysis to challenging open problems of theoretical meteorology, (ii) the development of related innovative structure detection and tracking techniques in the framework of visual data analysis, and (iii) the co-development of a CRC-wide broadened perspective on notions of coherence and persistence as they arise in turbulence and geophysical fluid dynamics as well as in the more abstract setting of the state space dynamics of high-dimensional dynamical systems.

Publications C06